Disc recording/reproducing apparatus

ABSTRACT

A disc recording and/or reproducing apparatus including a signal recording/reproducing section for recording and/or reproducing information signals on a disc 86 mm in diameter housed in a cartridge main body to form a disc cartridge, a loading mechanism for loading or unloading the disc cartridge on or from the signal recording/reproducing section and a control circuit controlling the recording/reproducing operation of the recording/reproducing section. The disc has a signal recording part divided into plural signal recording zones of substantially equal line recording density ac ross the inner and the outer peripheries of the disc. The signal recording/reproducing section, the loading mechanism and the control circuit are housed in a casing which is 101.6 mm or less in width, 150 mm or less in length and 25.4 mm or less in height and which is provided with a disc inserting opening. The apparatus may be reduced in size without decreasing the recording capacity.

This is a divisional of application Ser. No. 07/889,494, filed May 27,1992, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a disc recording and/or reproducing apparatushaving reduced sized for recording and/or reproducing informationsignals using a cartridge type disc cartridge in which a disc isaccommodated in a cartridge main body.

2. Description of the Related Art

There has hitherto been proposed a disc recording and/or reproducingapparatus for recording and/or reproducing information signals using adisc cartridge in which a disc, such as an optical disc or amagneto-optical disc, is accommodated in a cartridge main body.

The disc recording and/or reproducing apparatus includes a chassis onwhich there are mounted a loading unit for transporting the disccartridge to a predetermined loading position, a rotating driving unitfor holding and rotationally driving the disc in the disc cartridge atthe loading position and an optical head unit for writing and/or readinginformation signals on or from the disc held by the rotating and drivingunit.

The loading unit includes a cartridge holder for holding the disccartridge introduced into the recording/reproducing apparatus. Thecartridge holder, which may be moved vertically within the main body ofthe apparatus by means of a cam or the like, holds the disc cartridge ina parallel position with respect to the chassis. The loading unit firstshifts the disc cartridge, held by the cartridge holder, in a directionparallel to the major surface of the disc, that is parallel to thechassis. When the disc is brought to a position directly above therotating and driving unit, the loading unit shifts the disc cartridgevertically towards the chassis.

With the disc cartridge thus displaced towards the chassis, the dischoused in the disc cartridge is held by the rotating and driving unitprovided on the chassis.

The optical head unit is mounted on the chassis for facing the majorsurface, the signal recording surface, of the disc which is rotationallydriven by the rotating and driving unit. The optical head unit issupported for being moved radially and across the inner and outerperipheries of the disc. With the disc being rotated by the rotating anddriving unit and with the optical head unit being moved radially of thedisc, the light flux may be radiated by the optical head unit onsubstantially the entire signal recording surface of the disc, so thatinformation signals may be recorded on or reproduced from substantiallythe entire signal recording surface of the disc.

The optical head unit is also provided with an object lens drivingdevice for performing focusing and tracking servo operations for causingthe light flux radiated on the disc to follow deviations from ahorizontal plane or concentric positions caused by disc rotation. Theobject lens driving device supports an object lens converging andradiating the light flux by a supporting member formed of a flexiblematerial so that the object lens may be moved in two directions, that isin a direction along the optical axis and a direction perpendicularthereto. The object lens driving device also includes anelectro-magnetic driving device for moving the object lens in these twodirections. This electro-magnetic driving device includes a coil whichis mounted on a lens bobbin supporting the object lens and which issupplied with a driving current based on focusing and tracking errorsignals employed in the focusing servo and tracking servo operations,and a magnetic circuit for passing the magnetic flux through the coil.

In the above-described disc recording/reproducing apparatus, it isdifficult to simplify the construction and manufacture and to reduce thesize of the apparatus because of the complex structure of the loadingunit adapted for moving the disc cartridge in the horizontal andperpendicular directions.

Besides, it is also difficult with the above-mentioned disc recordingand/or reproducing apparatus to simplify the construction and reduce thesize of the optical head unit because the optical head unit needs to beprovided with the above-described object lens driving device.

It may be contemplated to use a small-sized disc to reduce the size ofthe disc recording and/or reproducing apparatus. However, if the disc ofthe smaller size be used for reducing the size of the disc recordingand/or reproducing apparatus, the recording capacity for the informationsignals is diminished, so that the advantages of a large capacityinformation storage device may be lost.

OBJECT AND SUMMARY OF THE INVENTION

In view of the above-depicted status of the art, it is an object of thepresent invention to provide a disc recording and/or reproducingapparatus which may be simplified in manufacture and reduced in size andconstruction without diminishing the recording capacity for informationsignals.

The present invention provides a disc recording and/or reproducingapparatus comprising signal recording/reproducing means including anoptical head means, external magnetic head generating means and rotatingdriving means, said signal recording/reproducing means rotationallydriving a disc 86 mm in diameter by said rotating driving means at aconstant angular velocity, said signal recording/reproducing meansradiating a light beam to said disc by said optical head means andapplying an external magnetic field to said disc by said externalmagnetic field generating means for recording information signals onsaid disc, said signal recording/reproducing means radiating the lightbeam to said disc by said optical head for reading information signalsfrom said disc, said disc being housed in a cartridge main body so thatthe information signals may be recorded or reproduced from outside, saiddisc having an information recording section divided from the innerperiphery towards the outer periphery into plural signal recordingregions having substantially equal line recording density, loading meansfor loading a disc cartridge on said signal recording/reproducing meansor unloading said disc cartridge from said signal recording/reproducingmeans, said disc cartridge comprising said disc accommodated in saidcartridge main body, and controlling means for controlling therecording/reproducing operation of said signal recording/reproducingoperation, said signal recording/reproducing means, said loading meansand said controlling means being housed in a casing which is 101.6 mm orless in width, 150 mm or less in length and 25.4 mm or less in heightand which is provided with a disc cartridge inserting opening on a frontside thereof.

In the disc recording and/or reproducing apparatus according to thepresent invention, the signal recording/reproducing section forrecording and/or reproducing information signals on or from a disc whichis 86 mm in diameter and which has a signal recording region dividedinto plural signal recording zones of substantially equal line recordingdensity across its inner and outer peripheries, loading means forloading or unloading a disc cartridge, which is the disc housed in acartridge main body, with respect to the signal recording/reproducingsection, and controlling means for controlling the recording and/orreproducing operation of said signal recording/reproducing section, arehoused in the casing which is sized as above and provided with the discinserting opening, so that the recording capacity is diminished and theapparatus may be reduced.

Other objects and advantages of the present invention will becomeapparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view showing a disc cartridge and anessential part of a disc recording and/or reproducing apparatus on whichthe disc cartridge is to be loaded.

FIG. 2 is a perspective view showing the state in which the disccartridge has been loaded on the disc recording and/or reproducingapparatus shown in FIG. 1.

FIG. 3 is an enlarged plan view showing the construction of an opticalpickup device of the disc recording and/or reproducing apparatus, with aportion thereof being broken away.

FIG. 4 is an enlarged side elevational view showing the state in whichthe disc cartridge has started to be introduced into the disc recordingad/or reproducing apparatus, with a portion thereof being broken away.

FIG. 5 is an enlarged side elevational view showing the state in whichthe operation of introducing the disc cartridge into the disc recordingand/or reproducing apparatus has been completed, with a portion thereofbeing broken away.

FIG. 6 is an enlarged side elevational view showing the state in whichthe operation of holding the disc cartridge introduced into the discrecording and/or reproducing apparatus has been completed, with aportion thereof being broken away.

FIG. 7 is an enlarged plan view showing the construction of a disc ofthe disc cartridge.

FIG. 8 is an enlarged schematic plan view showing a signal recordingstate on the disc.

FIG. 9 is an enlarged schematic plan view showing another signalrecording state on the disc.

FIG. 10 is a block diagram showing the construction of a controller inthe disc recording and/or reproducing apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, certain preferred embodiments will beexplained in detail.

In these embodiments, the disc recording and/or reproducing apparatus isdesigned as an apparatus for recording and/or reproducing informationsignals using a disc cartridge 101 having a magneto-optical discaccommodated in a cartridge main body, as shown in FIGS. 1 and 2.

Referring to FIG. 1, a disc cartridge 101 includes a magneto-opticaldisc 102 rotatably accommodated in a cartridge main body 108. Themagneto-optical disc 102 includes a disc substrate formed of alight-transmitting synthetic resin and a signal recording layer of amagnetic material deposited on one major surface of the disc substrate.The magneto-optical disc 102 has a diameter E shown in FIG. 7 which isequal to 86 mm. A hub-mounting opening 105 is formed at the center ofthe magneto-optical disc 102. A disc hub 106, by means of which themagneto-optical disc 102 is retained by a disc table 23 of the discrecording and/or reproducing apparatus according to the presentinvention, is mounted in the hub-mounting opening 105. The disc hub 106is formed of a magnetic material, such as metal, in the formsubstantially of a disk, and is mounted on the disc substrate of themagneto-optical disc 102 by welding or with the aid of an adhesive. Thedisc hub 106 is formed with a centering hole 107 having its centercoincident with the center of curvature of a spirally extendingsubstantially concentric recording track formed on the signal recordingsurface of the magneto-optical disc 102.

The cartridge main body 108 is made up of upper and lower halves abuttedand connected to each other to the shape of a thin casing capable ofaccommodating the magneto-optical disc 102. The upper major surface ofthe cartridge main body 108 is provided with an upperrecording/reproducing aperture 104 for laying to outside the signalrecording region on one major surface of the magneto-optical disc 102across the inner and outer peripheries of the disc. The lower majorsurface of the cartridge main body 108 is provided with a lowerrecording/reproducing aperture 110 for laying to outside the signalrecording region on the opposite major surface of the magneto-opticaldisc 102 across the inner and outer peripheries of the disc, as shown inFIG. 6. The lower recording/reproducing aperture 10 is formed at aposition in register with the upper recording/reproducing aperture 104on the lower surface of the cartridge main body 108 and has a sizesubstantially equal to that of the upper recording/reproducing aperture104.

The lower major surface of the cartridge main body 108 is provided witha chucking opening 109 via which the disc hub 106 of the magneto-opticaldisc 102 is laid to outside. The perimetral region of the chuckingopening 109 is formed with recesses engaged by abutting protuberances 68of the recording and/or reproducing apparatus according to the presentinvention.

A shutter member 103 is mounted on the cartridge main body 108. Theshutter member 103 is produced by bending a metal sheet or injectionmolding of a synthetic resin into the cross-sectional shape of a letterU for clampingly holding the upper and lower major surfaces at a lateralside of the cartridge main body 108. The shutter member 103 includes anupper plate section lying along the upper major surface of the cartridgemain body, a lower plate section extended parallel to the upper platesection and a connecting section connecting the proximal side of theupper plate section to that of the lower plate section. The shuttermember 103 is supported by the cartridge main body 108 for slidingmovement along the front side of the cartridge main body 108 contactedwith the connecting section. The upper and lower plate sections areformed with apertures located towards a lateral side of the shuttermember 103 along the direction of movement thereof relative to thecartridge main body 108.

When the shutter member 103 is not in use, that is, when it is at afirst position relative to the cartridge main body 108, therecording/reproducing apertures 104, 110 of the cartridge main body 108are closed by the upper and lower plate sections of the shutter member103. When the shutter member 103 is in use, that is, when it is at asecond position relative to the cartridge main boy 108, the apertures ofthe shutter member 103 are aligned with the recording/reproducingapertures 104, 110, so that these apertures 104, 110 are opened. Theshutter member 103 is resiliently biased by a spring member, not shown,provided within the cartridge main body 108, in a direction towards thefirst position of normally closing the recording/reproducing apertures104, 110.

The apertures of the shutter member 103 are formed to affect upper andlower lateral edges of the connection section. That is, the connectingsection of the shutter member 103 is of a narrower width at theapertures thereof than at the remaining portions of the connectingsection, which width is smaller than the thickness of themagneto-optical disc 102. On the other hand, the portion of thecartridge main body 108 in the vicinity of the rim of themagneto-optical disc 102 and the recording/reproducing apertures 104,110, that is the forward lateral side of the cartridge main body 108laid to outside via the apertures of the shutter member 103 on openingthe recording/reproducing apertures 104, 110, is of a thickness lessthan the thickness of the magneto-optical disc 102.

Referring to FIGS. 1 and 2, the disc recording and/or reproducingapparatus according to the present invention includes a casing 1 havinga bottom formed as a chassis 2 the forward side of which is opened. Theopened side of the casing 1 is closed by a front panel 24 having aslit-shaped disc cartridge inserting opening 25 via which the disccartridge 101 may be introduced.

The casing 1, inclusive of the front panel 24, is of a width, depth anda height, indicated by arrows Q, P and R in FIG. 2, respectively, equalto 70 mm or less, 100 mm or less and 24.5 mm or less, respectively.

A signal recording/reproducing section, including rotational drivingmeans, optical head means and magnetic field generating means, isprovided on the chassis 2 constituting the bottom plate of the casing 1.

Thus a spindle motor 3, constituting rotating and driving means forrotationally driving the disc 102 in the disc cartridge 101, is mountedon the chassis 2. The spindle motor 3 is mounted on an annular liftingblock 6 constituting loading means and which is provided with a centerhole 9 supporting the spindle motor 3 fitted therein. The lifting block6 includes a plurality of through-holes 8 each fitted with a slidebearing. A plurality of motor guide shafts 7, mounted upright on thechassis 2, are passed through these through-holes 8 so that the liftingblock 6 may be moved towards and away from the chassis 2 as indicated byarrows M, N in FIG. 6. Thus the spindle motor 3 may be moved towards andaway from the chassis 2. The spindle motor 3 has a spindle shaft 5,integral with a rotary shaft, substantially perpendicular to the chassis2. The spindle shaft 5 has its distal end directed upwards with respectto the chassis 2.

A disc table 4 is mounted on the rotary shaft of the spindle motor 3 forencircling the perimeter of the distal end of the spindle shaft 5. Thedisc table 4 is in the form of a disk having substantially the samediameter as the disc hub 106 for setting the disc hub 108 attached tothe magneto-optical disc. Between the spindle shaft 5 and the perimeterof the disc table 4, there is mounted an annular permanent magnet,integrally with the disc table 5, for magnetically attracting the dischub 106 of the magneto-optical disc 102 set on the disc table 4.

On the upper surface of the lifting block 6, there is mounted theabove-mentioned substantially annular cartridge-positioning member 67for encircling the disc table 4. At least three abutting protuberances68 are formed on the upper surface of the cartridge positioning member67. The upper ends of these protuberances 68 define a plane which iscloser to the chassis than and parallel to the disc hub setting plane ofthe disc table 4.

A lifting motor 11 for lifting the lifting block 6 and the disc table 4with respect to the chassis 2 is mounted in proximity to the spindlemotor 3 on the chassis 2. The lifting motor 11 is supported by a gearbox, not shown, mounted on the chassis 2. The gear box includes a camgear 13 meshing with a driving gear 12 mounted on a driving shaft of thelifting motor 11. The cam gear 13 is made up of a gear part 14 engagedwith the driving gear 12 for transmission of the driving force of thelifting motor 11, and a cam part 15. The lifting block 6 is engaged withand set on the cam part 15 and may be lifted by the cam part 15 onrotation of the cam gear 13. The lifting motor 11 is a stepping motorthe rotational angular position of which may be controlled accurately.The lifting block 6 is resiliently biased in a direction towards thechassis 2 by a tension coil spring 10 provided between the lifting blockand the chassis 2, so that the lifting block is pressedly engaged withthe cam part 15 of the cam gear 13.

The optical pickup device of optical head means, made up of an opticalblock 18 and an object lens driving device 17, is mounted on the chassis2 at the rear side of the spindle motor 3 when viewed in the insertingdirection of the disc cartridge 101 into the main body of the discrecording/reproducing apparatus. The optical pickup device is designedfor radiating a write-read light beam to the disc 102 set on the disctable 4.

Referring to FIG. 3, the optical block 18 includes a barrel blockhousing a laser diode 50 as a light source and a plurality of opticalcomponents for transmitting the light beam radiated from the laser diode50. Specifically, a diverging light beam, radiated by the laser diode 50in the optical block 18, is incident on a collimator lens 51. The lightbeam collimated by the collimator lens 51 is incident on a galvanomirror53 via a beam splitter prism. The galvanomirror 53 is controlled bycontrolling means as later described for deflecting and reflecting theincident parallel light beam based on predetermined control signals. Thecollimated light beam, reflected by the galvanomirror 53, is radiatedfrom the optical block 18 so as to be incident on the object lensdriving device 17.

The object lens driving device 17 includes a frame 17a and a pair ofguide shafts 63, 64 mounted within the frame 17a. These guide shafts 63,64 are mounted within the frame 17a so as to be parallel to each otherand to the frame 17a as well as being parallel to the chassis 2. A lensbobbin block 60 is mounted between these guide shafts 63, 64. Threeguide rolls 61, 62 each are provided on both lateral sides of the lensbobbin block 60 faced by the guide shafts 63, 64. At least one of theguide rolls 61 is supported by an arbor extended obliquely upwards at45° relative to the lens bobbin block 60, while the remaining guiderolls 61 are supported by arbors extended obliquely downwards at 45°relative to the lens bobbin block 60. These guide rolls 61, clampinglyholding the guide shaft 63, may be rolled on the guide shaft 63.Similarly to the guide rolls 61, the guide rolls 62 on the oppositelateral side of the lens bobbin block 60 are so supported that at leastone of the guide rolls 62 is supported by an arbor extended obliquelyupwards at 45° relative to the lens bobbin block 60, while the remainingguide rolls 62 are supported by arbors extended obliquely downwards at45° relative to the lens bobbin block 60. These guide rolls 62,clampingly holding the guide shaft 64, may be rolled on the guide shaft64.

The lens bobbin block 60 is moved in directions towards and away fromthe spindle motor 3 along the axes of the guide shafts 63, 64, asindicated by arrow L in FIGS. 1 and 3. That is, the lens bobbin block 60may be moved between the position of approaching the spindle motor 3 orthe radially inner position and the positing of being displaced from thespindle motor 3, or the radially outer position. The lens bobbin block60 is moved along the guide shafts 63, 64 by a feed motor (linear motor)provided within the frame 17a of the object lens driving device 17.

An object lens 55 is mounted on the upper surface of the lens bobbinblock 60. Within the lens bobbin block 60 is mounted a reflecting mirror54 for reflecting the collimated light beam incident from the opticalblock 18 back towards the object lens 55. Thus the collimated lightbeam, incident on the object lens driving device 17 from the opticalblock 18, is incident on the object lens 55 via reflecting mirror 54 andthereby rendered into a converged light beam, while being radiatedupwards away from the chassis 2 in parallel with the spindle shaft 5.

The light beam radiated from the object lens 55 and reflected from themagneto-optical disc 102 on the disc table 4 is again incident on theobject lens 55 and thereby rendered into a collimated light beam whichis incident on the reflecting mirror 54. The light beam re-incident onthe object lens 55 and thence transmitted to the reflecting mirror 54 isthereby reflected back towards the optical block 18. A photodetector fordetecting the light returned to the optical block 18 is provided withinthe block 18. The light beam returned from the object lens drivingdevice 17 to the optical block 18 is returned via galvanomirror 53 to abeam splitting prism 52 which causes the light beam from thegalvanomirror 53 to be incident on a Wollaston prism 56 withoutreturning the light to the collimator lens 51. The Wollaston prism iscomposed of two rectangular prisms of an optical material exhibitingoptical anisotropy, such as calcite or quartz, arranged with theiroptical axes perpendicular to each other. The light beam transmittedthrough the Wollaston prism 56 is transmitted through a light convergingconvex lens 57 and a multiple lens 58 having a concave surface and anopposite cylindrical surface so as to be received by a photodiode 59functioning as a light sensor.

Based on the detection output from the photodetector 59, focusing errorsignals are produced for indicating an amount of deviation along theoptical axis of the point of convergence of the light beam converged bythe object lens 55 from the signal recording surface of themagneto-optical disc 102. Similarly, tracking error signals indicatingan amount of deviation in a direction perpendicular to the optical axisof the object lens 55 between the above-mentioned point of convergenceand the recording track formed on the signal recording surface of themagneto-optical disc 102, and readout signals of information signalsread out from the recording track of the magneto-optical disc 102, areproduced.

Referring to FIGS. 1 and 4, a magnetic head device 66, functioning asexternal magnetic field generating means, is mounted on the lens bobbinblock 60 via a magnetic head supporting arm 19. The magnetic head device66 is adapted for applying an external magnetic field for writinginformation signals on the magneto-optical disc 102. The magnetic headsupporting arm 19 has its proximal end mounted on the lens bobbin block60 and has its mid part bent so that its distal end is faced by theobject lens 55. The magnetic head device 66 and the object lens 55 faceeach other with a distance in-between which is the sum of the thicknessof the magneto-optical disc 102 and the working distance of the objectlens 55 taking the amount of deviations from planarity of themagneto-optical disc 102 by the rotating and driving means taken intoaccount. The working distance of the object lens 55 is the distance fromthe foremost end of the object lens 55 to the focal point of the objectlens 55.

A cartridge holder 2 is arranged at a position above the chassis 2 inthe casing 1. The cartridge holder 28 is formed from a substantiallyplanar metal sheet having holding sections 29, 30 formed by bending bothlateral sides. These holding sections 29, 30 are in the shape of aletter U in cross-section at both lateral sides by bending the lateralsides twice at right angles. The cartridge holder 28 is arrangedparallel to the chassis 2 by having its lateral sides supported by theinner wall sections of the casing 1.

The cartridge holder 28 is so designed that the disc cartridge 101 maybe introduced into a space defined between the holding sections 29, 30from the front side. The disc cartridge 101 introduced between theholding sections 29, 30 has its lateral sides supported by these holdingsections 29, 30. Thus the disc cartridge 101, inserted via insertingopening 25, is introduced into a space between the holding sections ofthe cartridge holder 28.

The cartridge holder 28 is provided with a shutter opening lever 37 foropening the shutter member 103 of the disc cartridge 101. The shutteropening lever 37 has its proximal end supported by the rear side of thecartridge holder 28 for rotation about a pivot shaft 38 as a center ofrotation. A shutter opening pin 41 is set at the distal end of theshutter opening lever 37 for depending towards the chassis 2. Theshutter opening pin 41 is introduced into an arcuate slit 36 in theupper surface of the cartridge holder 28 so as to be intruded into thespace defined between the holding sections 29, 30. The shutter openingpin 41 is moved within the guide slit 36 by rotation of the shutteropening lever 37. The shutter opening lever 37 is rotationally biased ina direction of rotating the shutter opening pin 41 towards the frontside in a direction as indicated by arrow K in FIG. 1 by a torsion coilspring 39 having its coil part supported by pivot shaft 38. The torsioncoil spring 39 has its one arm retained by the shutter opening lever 37while having its opposite arm retained by a retention pawl 40 formedwith the cartridge holder 28. When the disc cartridge 101 is notinserted into the cartridge holder 28, the shutter opening pin 41 ispositioned at the forward initial position at the end of the arcuateguide slit 36. A plunger 20 is provided on the chassis 2 at a positioncorresponding to the mid part of the shutter opening lever 37 whenrotated towards rear by the disc cartridge 101 inserted into thecartridge holder 28. The plunger 20 plays the role of locking theshutter opening lever 37 against being returned from its rear positiontowards its forward initial position.

The control means for the disc recording and/or reproducing apparatus iscomprised of a control unit 70, as shown in FIG. 10. The control unit 70includes controlling circuits for controlling the operation of thespindle motor 3, optical pickup device or the magnetic head device 66 onthe basis of various input signals. More specifically, the controllingcircuit is formed by electronic components assembled on a printedcircuit board in a space defined between the inner surface of the casing1 and the cartridge holder 28 arranged in an upper part within thecasing 1. The control unit is supplied with operating signals enteredvia an input device manually operated from outside of the disc recordingand/or reproducing apparatus, output signals from the optical pickupdevice, detection signals indicating detected rotational velocity of thespindle motor 3 or the lifting motor 11, or detection signals indicatingthe end of insertion of the disc cartridge 101 into the cartridge holder28. In the present disc recording and/or reproducing apparatus, thetracking servo operation based on the driving of the galvanomirror 53 ofthe optical pickup device, the focusing servo operation based on thedriving control of the lifting motor 11 as later explained, or thespindle servo operation for controlling the rotational velocity of thespindle motor 3 so as to be constant, is performed on the basis ofcontrol signals from the control unit 70. A feed motor 65 feeds the lensbobbin block 60 radially across the magneto-optical disc 102 based onthe detection signals from the optical pickup device, while feeding theobject lens driving device 17 to a desired position on themagneto-optical disc 102 based on an accessing command supplied from thecontrol circuit 70 based on commands from e.g. a host computer.

In the present disc recording and/or reproducing apparatus, the outputlevel of the laser diode 50 is set to a playback level bycorrespondingly controlling a driving circuit 71 of the laser diode 50.The information signals read by the optical pickup device aretransmitted for demodulation to a modem circuit 72 controlled by thecontrol circuit 70. The signals demodulated by the modem circuit 72 arestored in a memory 73 controlled by the control circuit 70. The signalsstored in memory 73 are outputted to a variety of external devices viaan input/output controller 74 controlled by the control unit 70. Thesignals stored in memory 73 are outputted to a variety of externaldevices via a decoder 75 controlled by the control unit 70, while beingoutputted to a variety of output devices as analog audio signals via aD/A converter 76.

On the other hand, in the present disc driving and/or reproducingapparatus, information signals entered via a variety of external devicesare stored in memory 73 via input/output controller 74. Signals storedin memory 73 are transmitted to modem circuit 72 for demodulation. Thesignals modulated by the modem circuit 72 are supplied to a drivingcircuit 77 of a magnetic head 66 while being supplied to the drivingcircuit 71 of laser diode 50 for controlling the laser diode 50 forsetting the output level of the laser diode 50 to a recording level.Information signals are written on the signal recording surface of themagneto-optical disc 102 by this optical pickup device and the magnetichead device 66.

For loading the disc cartridge 101 into the disc recording and/orreproducing apparatus according to the present invention, the disccartridge 101 is inserted via the inserting opening 25 so as to be heldbetween the holding sections 29, 30. At this time, the disc cartridge101 is inserted with the shutter member 103 at the forward side, asshown by arrow J in FIG. 1.

The lower end of the shutter opening pin 41 is now abutted by the end ofthe connecting section of the shutter member 103 on the front side ofthe cartridge main body 108. When the disc cartridge 101 is furtherinserted into the inside of the holding sections 29, 30, the shutteropening pin 41 is thrust by the cartridge main body 108 for rotating theshutter opening lever 37 against the bias of the torsion coil spring 39towards the rear side of the main body of the apparatus. At this time,the shutter opening pin 41 thrusts the connecting part of the shuttermember 103, while being moved along guide slit 36, for opening therecording/reproducing apertures 104, 110 by the shutter member 103. Whenthe recording/reproducing apertures 104, 110 are opened by the shuttermember 103, the forward sides of the apertures of the shutter member 103are located substantially in the center of the forward side of thecartridge main body 108. At this time, the forward side of the cartridgemain body 108 is laid to outside via the apertures of the shutter member103, as shown in FIG. 4.

The disc cartridge 101, inserted towards the rear of the main body ofthe apparatus, is moved towards the rear of the apparatus, while beingthrust and supported towards the chassis 2 by the cartridge thrustingsprings 31 to 34. During this time, the narrow portion of the connectionpart of the shutter member 103 is passed through a space between theobject lens 55 and the magnetic head device 66, the forward side of thecartridge main body 108 is then passed through the space between theobject lens 55 and the magnetic head device 66 and finally the disc 102is introduced into the space between the object lens 55 and the magnetichead device 66. Since the space between the object lens 55 and themagnetic head device 66 is set so as to be wider than the thickness ofthe magneto-optical disc 102, the disc 102 is introduced into the spacebetween the object lens 55 and the magnetic head device 66 without beingabutted against the object lens 55 or the magnetic head device 66. Theshutter opening lever 37 is locked by the plunger 20 at a position inwhich the shutter opening pin 41 is at the rear side. The lifting block6 is urged by the tension coil spring 10 towards the chassis 2 so as tobe positioned at an initial position.

When the disc cartridge 101 is introduced to a predetermined insertioncomplete position within the apparatus, the disc table 4 and the dischub 106 face each other at a substantially coaxial position, as shown inFIG. 5. The insertion of the disc cartridge 101 to its insertioncomplete position is sensed by a detecting lever 45 and the detectiondevice 42 so that a corresponding detection signal is transmitted to thecontrol device 70. The detecting lever 45 and the detection device 42are mounted on the chassis 2 at the rear side of the cartridge holder28. The detection lever 45 is mounted for sliding in a fore and aftdirection by a detection lever supporting member 44 mounted on thechassis 2 with the foremost part of the lever 45 being directed forwardsin the vicinity of the rear end of the cartridge holder 28. Thedetection lever 45 is positioned at an initial forward position underthe bias of a compression coil spring, not shown. When the disccartridge 101 is introduced into the cartridge holder 28, the detectionlever 45 is thrust by the cartridge main body 108 of the disc cartridge101 and thereby slid rearwards. The detection device 42 includes e.g. aphotocoupler for detecting entrance of an object into a slit 43 byoptical or the like means. The detection device 42 is arranged at aposition such that, when the disc cartridge 101 is inserted to a presetposition in the apparatus, the shutter opening lever 37 rotated by thecartridge main body 108 of the disc cartridge 101 is partially intrudedinto the slit 43.

The controlling device 70, supplied with detection signals from thedetection device 42, actuates the lifting motor 11, so that the cam gear13 is rotated by means of the driving gear 12 and hence the liftingblock 6 is moved upwards away from the chassis 2, as shown by arrow N inFIG. 6. That is, when the disc cartridge 101 is introduced to apredetermined position into the cartridge holder 28, the spindle motor 3is moved by the lifting motor 11 from a non-rotating driving position inwhich the spindle motor is spaced apart from the disc 102 to a rotatingdriving position in which the spindle motor is closer to the disc 102than at the non-rotating driving position. When the lifting block 6 islifted to the rotating driving position, the disc hub 106 of the disc102 is set on the disc table 4, while the cartridge main body 108 is seton the cartridge body positioning member 67, as shown in FIG. 6. Thedistal end of the spindle shaft 5 is fitted at this time in thecentering hole 107. At this time, the abutment protuberances 68, 68, 68of the positioning member 67 are abutted against positioning recesses67, 67, 67 formed around the rim of the chucking opening 109 of thecartridge main body 108.

The cartridge main body 108, thus set on the cartridge positioningmember 67, is moved in the space defined between the holding sections29, 30 in a direction away from the chassis 2 against the bias of thecartridge thrusting springs 31 to 34. Besides, with the disc hub 106thus set on the disc table 4, the magneto-optical disc 102 is spacedapart from the inner wall of the cartridge main body 108. Since thedistance between the upper surface of the disc table 4 and the abuttingprotuberances 68 of the positioning member 67 is always constant, themagneto-optical disc 102 is maintained at a constant position withrespect to the cartridge main body 108. The disc hub 106 is kept inpressure contact with the disc table 4 under the force of magneticattraction exerted by a permanent magnet provided on the disc table 4.

When the spindle motor 3 is driven in this state, the disc 102 isrotationally driven simultaneously with the disc table 4 at a constantangular velocity by the spindle motor 3. On the other hand, the opticalpickup including the optical block 18 and the lens bobbin block 17 andthe magnetic head device 66 write information signals on themagneto-optical disc 102, rotationally driven by the spindle motor 31,by applying an external magnetic field and simultaneously radiating alight beam on the disc 102, while reading information signals previouslyrecorded on the disc by radiating the light beam on the disc.

As stated above, the cam part 15 of the cam gear 13 includes a sectionfor holding the disc 102 on the disc table 4 and a section for adjustingthe height of the disc cartridge 101 after the end of the holdingoperation. The holding section of the cam part 15 has a cam profile suchthat the lifting block 6 is moved steeply to a predetermined height,while the height adjusting section of the cam part 15 has a cam profilesuch that the lifting block 6 may be moved within a minor distance. Thecam gear 13 is provided with a rotary encoder, not shown, for detectingthe rotational angular position of the cam gear 13. The rotary encodergenerates detection signals for calculating the rotational velocity andthe angular position of rotation of the cam gear 13.

With the magneto-optical disc 102 thus set on the disc table 4, thelifting motor 11 may be raised and lowered within a minor movement stepof the order of e.g. 1 μm with respect to the lifting block 6. Thus,with the present disc driving and/or reproducing apparatus, by raisingor lowering the lifting block 6 by the lifting motor 11 by minor stepsof movement, with the disc 102 set on the disc table 102, themagneto-optical disc 102 may be adjusted at all times so as to be at apredetermined position relative to the object lens 55.

In this manner, by driving the lifting motor 11 based on the focusingerror signals produced by the optical pickup device, the signalrecording surface of the magneto-optical disc 102 may be set at alltimes on the focal point of the light beam formed by the object lens 55by way of performing a focusing servo operation. Thus there is nonecessity of providing an object lens driving device, that is anactuator, for moving the object lens 55 along the optical axis, in theoptical pickup of the disc recording and/or reproducing apparatus.

Meanwhile, the signal recording region formed on the signal recordingsurface of the magneto-optical disc is divided into plural sub-regionsfrom the inner towards the outer periphery. That is, the inner mostsub-region of the signal recording region is a first zone A. A secondzone B is formed contiguous to and on the outer side of the first zoneA. A third zone C is formed contiguous to and on the outer side of thesecond zone B. A fourth zone D is formed contiguous to and on the outerside of the third zone C. In these zones A to D, digitized informationsignals are written in the form of pits, as shown in FIG. 8. These pits,corresponding to these information signals, are formed by minuteprojections, recesses or through-holes or as differences in thedirection of magnetization in the signal recording layer of a magneticmaterial deposited on the disc substrate of the magneto-optical disc102. These pits are so formed that the minimum pitch is 0.6 μm. Clocksignals for servo are also written in the zones A to D.

In these zones A to D of the magneto-optical disc 102, the pitscorresponding to the information signals are written at a substantiallyequal line recording density. Since the disc 102 is rotated at aconstant angular velocity by the spindle motor 3, the frequencies of thedigital signals corresponding to the pits formed in these zones A to Dbecome higher towards the outer periphery of the disc, that is in theorder of the zones A to D. The above-mentioned clock signals for servoare written so as to be read at a constant clock frequency f₁ across theinner and outer peripheries of the signal recording region.

In the present disc recording and/or reproducing apparatus, the clocksignals for servo are used as channel clock signals having frequenciesequal to af₁, a being a frequency conversion ratio associated with theeach of zones A to D. The frequency conversion ratio a is set so as tohigher towards the outer periphery of the disc, that is in the order ofthe zones A to D. That is, the frequency of the channel clock signalsaf₁ is selected so as to be higher towards the outer zones and lowertowards the inner zones so as to be proportionate to the frequency ofthe digital signals written and read in these zones A to D. With thepresent disc recording and/or reproducing apparatus, since the frequencyaf₁ is proportionate to the frequency of the digital signals, digitalsignals may be written and read on the magneto-optical disc 102 based onthese channel clock signals. About 430 megabytes (MB) at the maximum ofthe information may be recorded on the disc 102.

In the present disc recording and/or reproducing apparatus, since thesignal recording region of the magneto-optical disc 102 is divided intoplural zones, in which the pits are formed at substantially the constantline recording density, and the disc 102 is adapted for beingrotationally driven at a constant angular velocity, the recordingdensity of the information signals on the magneto-optical disc 102 maybe improved without complicating the construction of the apparatus. Thatis, if the pits are formed at a constant line density and the frequencyof the digital signals read from the magneto-optical disc 102 is to beconstant across the inner and outer peripheries of the disc, it becomesnecessary to rotate the magneto-optical disc 102 so that the disc isrotated at a constant linear velocity at a portion of the disc faced bythe object lens, thus complicating the structure. On the other hand, ifthe magneto-optical disc 102 is rotated at a constant angular velocityand the frequency of the digital signals read from the magneto-opticaldisc 102 is to be constant across the inner and outer peripheries of thedisc 102, it is necessary to set the line density so as to be lowertowards the outer disc periphery, so that the recording density of theinformation signals on the magneto-optical disc 102 cannot be increased.

The construction of the disc recording and/or reproducing apparatusaccording to the present invention is not limited to that shown in theabove embodiment. For example, a mechanism of lifting the cartridgeholder 28 holding the disc cartridge 101 may be used as loading means inplace of the mechanism of lifting the spindle motor 3.

Also, in the optical pickup in the present disc recording and/orreproducing apparatus, the so-called tracking servo, in which the lightbeam radiated from the object lens 55 is caused to follow periodicmovements of the recording tracks along the radius of the disc due tooffsetting of the magneto-optical disc 102 caused by rotation of themagneto-optical disc 102, is achieved by deviating the light beamincident on the object lens 55 by the galvano-mirror 53. However, thetracking servo may also be realized by moving the lens bobbin block 60along the pickup guide shafts 63, 64 or by supporting only the objectlens 55 by the object lens driving device for moving the light fluxalong the radius of the magneto-optical disc 102 with respect to thelens bobbin block 60.

In the present disc recording and/or reproducing apparatus, as describedabove, a signal recording and/or reproducing section for recordingand/or reproducing information signals on or from a magneto-optical discof 86 mm in diameter, accommodated in a cartridge main body, and havingits signal recording section divided into plural signal recordingregions having a substantially equal line recording density, loadingmeans for loading and/unloading the disc cartridge, which is amagneto-optical disc accommodated in a cartridge main body, with respectto the signal recording and/or reproducing section, and controllingmeans for controlling the recording/reproducing operation of the signalrecording/reproducing section, are housed in a casing which is 101.6 mmor less in width, 150 mm or less in length and 25.4 mm or less in heightand which is provided with a disc cartridge inserting opening.

The result is that, with the present disc recording and/or reproducingapparatus, the apparatus may be reduced in size without decreasing therecording capacity.

Also, with the present disc recording and/or reproducing apparatus, discrotating and driving means may be moved by movement means from thenon-rotating driving position spaced apart from the magneto-optical discto the rotating driving position in which the rotating and driving meansis located closer to the disc than at the non-rotating driving positionupon completion of loading of the disc cartridge by the loading means.

Thus, with the present disc recording and/or reproducing apparatus, theabove-mentioned loading means and hence the disc recording and/orreproducing apparatus may be simplified in construction.

What is claimed is:
 1. A magneto-optical disc recording and reproducingapparatus comprising:an outer casing including at least a lower chassis;rotational driving means within the outer casing for driving amagneto-optical disc at a substantially constant angular velocity, thedisc being housed within a disc cartridge and having a substrate and asignal recording region formed on the substrate, the signal recordingregion containing a plurality of concentric signal recording zoneslocated at increasing radial distances from the center of the disc, eachsignal recording zone having a substantially equal line recordingdensity and containing servo clock signals encoded such that lineardistances between the servo clock signals along circular tracks of thedisc increase as the radial distance of each track from the center ofthe disc increases, whereby the servo clock signals recorded atdifferent radial distances from the center of the disc are reproduced ata substantially constant frequency; optical means for radiating a lightbeam onto the disc and for receiving light returning from the disc;magnetic head means for applying a magnetic field onto the disc whenrecording information signals on the disc; magnetic head support meansfor supporting the magnetic head means, the magnetic head support meansbeing attached to the optical means so that the magnetic head means movein unison with the optical means; loading means for loading the disccartridge into the disc recording and reproducing apparatus, and forunloading the disc cartridge from the disc recording and reproducingapparatus; and controlling means for controlling the rotational drivingmeans, the optical means, and the magnetic head means, the controllingmeans modifying the servo clock signals to form a plurality of channelclock signals for reproducing and recording signals in the signalrecording zones, each signal recording zone having one correspondingchannel clock signal such that the frequencies of the channel clocksignals of the signal recording zones located at larger radial distancesfrom the center of the disc are higher than the frequencies of thechannel clock signals of signal recording zones located at smallerradial distances from the center of the disc.